A typical heavy truck frame includes two elongated frame rails joined by cross members to form a generally rectangular structure. Other components are mounted to or supported by the frame, including the bumpers, the engine and transmission, and the front and rear axles and suspensions.
It would be advantageous to design and make a commercial vehicle frame comprising various structural segments or units, each designed for the load or service demands placed on the commercial vehicle frame. Such an approach allows for improvements in assembly and service, including the use of modular frame units, which can be assembled elsewhere and brought as a unit to the assembly line. In addition, a segment approach allows for the redesign of the frame to decrease weight, which can improve fuel mileage of the vehicle. Moreover, frame segments of various materials and material properties (e.g., stiffness, weight) may be selected, with segments located along the frame's length to achieve an appropriate combination of mass, strength and durability.
Each frame segment, unit, or module within the frame requires at least one structural interface or joint with another segment, unit or module. To be successful, the interface must be structurally secure for joint integrity and durability.
For the purposes of manufacturing efficiency and aftermarket serviceability, it is advantageous if the interface joint is easily assembled and disassembled.
Typically, a structural joint interface in a commercial vehicle frame is assembled with rivets, welds, or bolts and nuts. Rivets and welding are generally considered “permanent” structural joints, as disassembly of such joints involves significant effort and usually to some degree destruction of the joint and/or the fastener system. In structural interface joints in very high loading conditions rivets are heavily favored in the industry. Bolts and nuts, on the other hand, which can be removed without harm to the frame members or fasteners, are not considered permanent, which is an advantage in service and repair and in conversion of a truck frame from one purpose to another. However, bolts and nuts are not usually considered to be as secure as rivets.
The invention provides a system for joining members of a vehicle frame in a highly secure manner while also providing the ability to readily disassemble the joint. A feature of the invention is an interface system that is formed or provided on mating surfaces of the frame components. The interface system includes mating surfaces shaped to interengage to resist linear and rotational shear forces at the mating surfaces of the parts.
A releasable structural joint for frame members in a vehicle, according to an embodiment of the invention includes a first frame member having a first contoured interface surface, a second frame member having a second contoured interface surface complementary to the contoured interface surface of the first frame member, and a plurality of releasable fasteners for releasably fastening the second frame member to the interface plate, wherein, the contoured interface surfaces interengage to resist linear and torsional shear forces.
According to the invention, the contoured interface surfaces of the first frame member and the second frame member each include a plurality of protrusions and depressions. The protrusions and depressions may be formed as bumps and dips in the surface or as ridges and grooves, or as other complementary engaging shapes.
According to one embodiment, the contoured interface surfaces of a first frame member and a second frame member each include at least one ridge and one groove, the at least one ridge on each contoured interface surface aligning with the at least one groove on the other contoured interface surface. More preferably, the contoured interface surfaces each comprise a plurality of parallel ridges and grooves.
The contoured interface surfaces of the first frame member and the second frame member each has a longitudinal direction and may include at least one pair, and preferably a plurality, of ridges and grooves obliquely oriented to the longitudinal direction.
The contoured interface surfaces of the first frame member and the second frame member may each include at least one longitudinally directed ridge and groove and at least one obliquely oriented ridge and groove.
According to another aspect of the invention, the contoured interface surfaces of the interface plate and the contoured interface surface of the second frame member are formed of different materials having different hardness values.
According to yet another aspect of the invention one contoured interface surface is formed on a plate permanently mounted to a frame member.
According to another embodiment, the contoured interface surfaces of the first frame member and the second frame member each include concentrically arranged grooves and ridges and a plurality of linearly arranged grooves and ridges.
According to the invention, a truck frame having a releasable structural joint, includes a first frame member, an interface plate mounted to the first frame member, the interface plate having an interface surface contoured with a plurality of protrusions and depressions, a second frame member mounted to the first frame member, the second frame member having an interface surface contoured with a plurality of protrusions and depressions complementary to the plurality of protrusions and depressions of the interface surface of the interface plate, and, a plurality of releasable fasteners for releasably fastening the second frame member to the interface plate, wherein, the contoured interface surfaces interengage to resist linear and torsional shear forces.